Summary of findings for the main comparison. Anti-leukotrienes & ICS versus same dose ICS for asthma

Anti-leukotrienes and inhaled corticosteroids versus same dose of inhaled corticosteroids

Patient or population: Children with asthmaSettings: OutpatientsIntervention: Anti-leukotrienes and inhaled corticosteroids

Comparison: Same dose of inhaled corticosteroids

Outcomes

Illustrative comparative risks* (95% CI)

Relative effect(95% CI)

Number of participants(studies)

Quality of the evidence(GRADE)

Comments

Assumed risk

Corresponding risk

Control

Anti-leukotrienes and inhaled corticosteroids versus same dose of inhaled corticosteroids

Participants with one or more exacerbations requiring oral corticosteroids

Follow-up: mean 4 weeks

See comment

See comment

Risk Ratio

0.80 [0.34, 1.91]

279(1 study)

⊕⊕⊝⊝low¹

Single study reported the primary outcome

No significant group difference with wide confidence interval

Participants with exacerbations requiring hospital admission

Follow-up: mean 4 weeks

See comment

See comment

Not estimable

279(1 study)

⊕⊝⊝⊝very low²

Single study reported the outcome (but no admissions were reported)

Change from baseline FEV₁ (%)

Follow-up: mean 4 weeks

3.3% increase from baseline FEV₁ on placebo

4.6% [ 2.4%, 6.0%]

1.30% [-0.09%, 2.69%]

279(1 study)

⊕⊕⊝⊝low¹

Single study reported the outcome

No significant group difference with wide confidence interval

*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in the footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI)CI: Confidence interval

GRADE Working Group grades of evidenceHigh quality: Further research is very unlikely to change our confidence in the estimate of effectModerate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimateLow quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimateVery low quality: We are very uncertain about the estimate

¹ Single study, wide confidence interval² There were no admissions to hospital in this study

Description of the condition

Asthma is the most common chronic disease of childhood and is one of the leading reasons for emergency department visits (Linzer 2007) and hospitalisations (PHAC 2007). It affects an estimated 235 million individuals worldwide (WHO 2011). Asthma presents as recurrent episodes or persistent symptoms of reversible airway obstruction. It is a complex syndrome that involves bronchospasm, inflammation, secretions, and airway hyperresponsiveness (Busse 2006).

Increasing the dose of ICS is effective, but may be associated with short-term growth suppression in a dose-related, and probably a drug-dependant, fashion in children (de Benedictis 2001; Eid 2002; Sharek 1999). The efficacy of LABAs as adjunct to ICS has been thoroughly evaluated recently (Heuck 2000; Malone 2005; Pohunek 2006; Stelmach 2008). Concerns have been raised about the efficacy of LABAs in children and possibly their safety, not only when used as a monotherapy, which is no longer recommended, but also as adjunct therapy (Cates 2008; Cates 2012). Although the risk of serious adverse events of regular formoterol in children was greater than that observed in adults, the difference between age groups did not reach statistical significance (Cates 2008).

Anti-leukotriene agents (also know as leukotriene receptor antagonists or LRTA) are anti-inflammatory drugs that interfere either with leukotriene production (5-lipoxygenase inhibitors) or with receptors (leukotriene receptors antagonists) (Calhoun 2001). They have the advantage of being administered orally in a single or twice-daily dose, and importantly, they seem to lack some of the dose-dependent adverse effects associated with long-term ICS, such as growth and adrenal suppression (Muijsers 2002). Anti-leukotrienes have the potential to interfere with the pathophysiology of asthma and improve to some extent the clinical and functional manifestations of asthma (Chauhan 2012; Paggiaro 2011).

Why it is important to do this review

A 2004 Cochrane review (Ducharme 2004) evaluating the addition of anti-leukotrienes to ICS in children and adults with asthma identified only two paediatric trials, one of which was published as an abstract and did not contribute data to the meta-analysis. In the past decade, several additional trials were published that may shed more light on the role of anti-leukotrienes as adjunct therapy to ICS. The original review is not being updated; instead, it has been replaced by the present systematic review in children; a second review pertaining to adults will follow.

To compare the efficacy and safety of the combination of anti-leukotriene agents and ICS to the use of the same, an increased, or a tapering dose of ICS in children and adolescents with persistent asthma who remain symptomatic despite the use of maintenance ICS. In addition, we wished to determine the characteristics of people or treatments, if any, that influenced the magnitude of response attributable to the addition of anti-leukotrienes.

Criteria for considering studies for this review

Types of studies

We considered for inclusion all randomised controlled trials (RCTs) with either parallel group or cross-over design.

Types of participants

We included children and adolescents aged one to 18 years with persistent asthma who remained symptomatic despite the use of a stable maintenance of ICS (or who were made symptomatic after ICS dose reduction).

Types of interventions

We focused analysis on the following three treatment protocols:

Anti-leukotrienes and ICS (step 3) versus the same dose of ICS (step 2).

We did not permit cointerventions other than rescue beta₂-agonists and oral corticosteroids.

Types of outcome measures

Primary outcomes

The number of participants with one or more exacerbations requiring oral corticosteroids (unless both groups were tapering their dose of ICS, in which case, the main outcome was the change from the baseline dose of ICS required to maintain control).

Secondary outcomes

Exacerbations:

participants with one or more exacerbations leading to a hospital admission; and

participants with one or more exacerbations leading to an emergency department or an acute-care visit.

Clinical or physiologic outcomes reflecting chronic asthma control including the following:

Search methods for identification of studies

Electronic searches

We identified trials from the Cochrane Airways Group Specialised Register of Trials (CAGR), which is maintained by the Trials Search Co-ordinator for the Group. The Register contains trial reports identified through systematic searches of bibliographic databases including the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, PsycINFO, AMED (Allied and Complementary Medicine Database), and CINAHL (Cumulative Index to Nursing and Allied Health Literature); and the handsearching of respiratory journals and meeting abstracts (please see Appendix 1 for further details). We searched all records in the CAGR coded as 'asthma' using the following terms:

(leukotriene* or leucotriene* or anti-leukotriene or anti-leucotriene or montelukast or singulair or zafirlukast or accolate or pranlukast or azlaire)

AND (((steroid* or corticosteroid* or glucocorticoid*) AND inhal*) OR (fluticasone or beclomethasone or budesonide or triamcinolone or flunisolide or ciclesonide or bronalide or becotide or azmacort or aerobid or flixotide or aerobec or flovent or becloforte or pulmicort or beclovent or vanceril or alvesco))

AND (child* or paediat* or pediat* or adolescen* or infant* or toddler* or bab* or young* or *school* or newborn* or "new born*" or new-born* or neo-nat* or neonat*)

The search was conducted up to January 2013. There was no restriction on language of publication.

Searching other resources

We checked the clinicaltrials.gov and various pharmaceutical companies' websites for the relevant trials.

Data collection and analysis

Two reviewers (BFC and RBS) independently collected data for analysis.

Selection of studies

Two reviewers (BFC and RBS) reviewed each abstract and annotated them as follows:

clearly an eligible RCT;

clearly not eligible; or

unclear.

We obtained full papers for all those that were clearly an eligible RCT and for those in whom the design or relevance was unclear. We contacted authors to confirm the missing information on selection criteria.

Data extraction and management

Two reviewers (BFC and RBS) independently extracted data and dealt with disagreement by consensus and with the input of a third reviewer (FMD), if needed.

Assessment of risk of bias in included studies

The methodological quality of eligible controlled trials was assessed using The Cochrane Collaboration's 'Risk of bias' tool based on six criteria: random sequence generation, allocation concealment, blinding, incomplete outcome data, selective reporting, and other bias. Two reviewers (BFC and FMD) independently assessed methodological quality and deemed a study to have a high methodological quality if the reported randomisation procedures and blinding were adequate and there was a low and balanced group attrition.

Measures of treatment effect

We calculated treatment effects for dichotomous variables as odds ratios (OR), relative risk (RR), risk difference (RD), or a combination of the aforementioned. For continuous outcomes, such as the pulmonary function test, we calculated pooled statistics as mean differences (MD), generic inverse variance (GIV), or standardised mean differences (SMD), as indicated. We summarised differences between groups in event rates using rate ratio. We reported all estimates with 95% confidence intervals (CI). We assumed equivalence if the relative risk estimate and its 95% CI were between 0.9 and 1.1.

Unit of analysis issues

The unit of analysis was the participant.

Dealing with missing data

We did not impute missing data. We planned to contact authors to ask for missing data.

Assessment of heterogeneity

We tested the homogeneity of effect sizes between studies being pooled with the DerSimonian & Laird method, with P > 0.05 or an I² statistic > 40% used as the cut-off level for significance. If one or both methods suggested heterogeneity, we applied a random-effects model to the summary estimates. Unless specified otherwise, we used the fixed-effect model.

Assessment of reporting biases

We examined the funnel plot on the main outcome and conducted the Egger test (Egger 1997) to explore the possibility of bias.

Data synthesis

We reported all effect estimates with their 95% CI. We performed meta-analysis using Review Manager 5.2 (RevMan) (Higgins 2008; RevMan 2011).

Subgroup analysis and investigation of heterogeneity

We planned subgroup analyses to explore possible reasons for heterogeneity between study results on the primary outcome. We based a priori defined subgroups upon the following:

daily dose of ICS in both groups in hydrofluoroalkane beclomethasone dipropionate or equivalent (HFA-BDPeq) (for children aged six to 11 years, ≤ 200, 201 to 400, and > 400 μg HFA-BDPeq were considered as low-, medium-, and high-dose, while for adolescents aged 12 to 18 years, ≤ 250, 251 to 500, and > 500 μg HFA-BDPeq were considered as low-, medium-, and high-dose (Lougheed 2012));

Sensitivity analysis

For the primary outcome, we planned to perform two sensitivity analyses to determine the effect of publication status (abstracts or web reports only versus full peer-reviewed papers) and methodological quality, respectively. We explored a possible publication bias by removing trials not published as full text (i.e. abstracts or web reports) and bias due to poor methodological quality by removing trials not meeting all of the three following criteria: clearly reported and acceptable random sequence generation, blinding procedure, and balanced and low attrition in both groups.

'Summary of findings' tables

We included a summary of findings table for the two main comparisons in this review. We rated the quality of evidence using recommendations developed by the GRADE working group, presenting our ratings alongside the relative and absolute effects for the following outcomes:

Description of studies

Results of the search

The literature search conducted until January 2013 yielded 309 citations. The reasons for exclusion of various trials are available in the 'Excluded studies' section. We reported the flow of references in a PRISMA diagram (Figure 1).

The included trials were all published as full-text manuscripts and comprised 559 children (aged ≥ six years) and adolescents with mild to moderate asthma. Three trials compared the combination of anti-leukotrienes and ICS with the same dose ICS (Simons 2001; Stelmach 2007; Stelmach 2008), and one trial compared the combination of anti-leukotrienes and ICS with a higher dose ICS (Lemanske 2010). We did not identify studies that assessed the combination of anti-leukotrienes and ICS as a means to taper the dose of ICS.

Design: Two trials (Stelmach 2007; Stelmach 2008) used a parallel group design, while the remaining two trials used a cross-over design.

Participants: Included trials described a gender ratio ranging from 65% to 69% male. One trial (Simons 2001) recruited children aged six to 14 years while remaining trials enrolled children aged ≥ six years and adolescents. Stelmach 2007 enrolled children with moderate airway obstruction, and Lemanske 2010 enrolled children with mild to moderate airway obstruction. The remaining two trials did not report the severity of airway obstruction. Stelmach 2007 and Stelmach 2008 recruited children who had confirmed positive skin-prick tests for specific allergens. Both studies compared the combination of anti-leukotriene and ICS to the same dose ICS.

Intervention duration: The duration of intervention varied from four to 16 weeks.

Intervention drugs: All trials used montelukast (anti-leukotriene agent) at a dose of 5 mg for children aged six to 14 years and 10 mg for adolescents aged 15 years and above. Three trials used budesonide turbuhaler (Simons 2001; Stelmach 2007; Stelmach 2008), and the remaining trial (Lemanske 2010) used fluticasone metered-dose inhaler.

Cointervention: No trials reported the use of additional antiasthmatic drugs, other than rescue beta₂-agonists and systemic corticosteroids.

Outcomes: Two cross-over trials (Lemanske 2010; Simons 2001) comparing the addition of anti-leukotriene agent to ICS with the same dose or higher dose of ICS, respectively, reported the primary outcome, the number of participants experiencing one or more exacerbations requiring rescue oral corticosteroids.

A small number of trials reported other measures of asthma exacerbation (hospital admissions), lung function (FEV₁, morning PEFR) and asthma control indices (change from baseline in daily use of beta₂-agonists, change in quality of life), and biological markers of inflammation (change from baseline in blood eosinophil counts). All four trials contributing data reported withdrawals and adverse effects.

Excluded studies

Of 309 citations, we excluded 303 citations for the following exclusive reasons: duplicate references (N = 32); not a randomised controlled trial (N = 18); participants did not have asthma (N = 1); the control intervention was not ICS (N = 87); the test intervention was not a combination of ICS and anti-leukotriene (N = 104); participants received non-permitted co-interventions (N = 8); the tested intervention was administered for less than four weeks (N = 3); participants had an acute exacerbation (N = 2); the age of participants was more than 18 years (N = 45); participants were naive to daily ICS before enrolment in the study (N = 2); and inadequate information was available for selection criteria (N = 2). The 'Characteristics of excluded studies' tables provide reasons for exclusion.

Risk of bias in included studies

The 'Characteristics of included studies' tables give full details of the risk of bias for each included trial, with a graphical summary of the 'Risk of bias' judgements in Figure 2. Three of the five included trials provided enough information to assess the method of randomisation.

Figure 2. 'Risk of bias' summary: review authors' judgements about each 'Risk of bias' item for each included study

Allocation

Three of the five trials provided sufficient information to confirm the adequacy of the allocation concealment.

Blinding

The procedures for blinding described in the trial reports were sufficient for us to judge that all the included studies were at a low risk of performance and detection bias..

Incomplete outcome data

All trials reported the number and reasons of withdrawals. We did not observe high or imbalanced withdrawal rate in any comparing groups.

Selective reporting

All trails reported all outcomes as mentioned in the methodology section of the published manuscript without any apparent bias.

Other potential sources of bias

We did not identify any other significant source of bias in included trials.

There was no statistically significant group difference in the only trial reporting the risk of children (aged six to 14 years) with exacerbations requiring oral corticosteroids over 12 weeks. There were eight children with an exacerbation on anti-leukotrienes, 10 on placebo, and one child who had an exacerbation on both treatments (N = 268 participants; risk ratio (RR) 0.80, 95% CI 0.34 to 1.91; Analysis 1.1; Figure 3). Because of the lack of trials reporting the primary outcome, we did not perform subgroup analysis, funnel plot, and sensitivity analysis.

Figure 3. Forest plot of comparison: 1 Anti-leukotrienes and ICS versus same dose of ICS, outcome: 1.1 Participants with one or more exacerbations requiring oral corticosteroids

Secondary outcomes

Exacerbations

The only trial that reported this outcome (Analysis 1.2) did not admit any participant to hospital with either treatment strategy due to asthma exacerbation.

Lung functions

No significant group difference was observed in the only trial reporting change from baseline FEV₁ (%) (N = 251 participants; mean difference (MD) 1.30, 95% CI -0.09 to 2.69; Analysis 1.3). Change from baseline in AM PEFR (N = 218 participants; MD 9.70 L/min, 95% CI 1.27 to 18.13; Analysis 1.4) and change from baseline in PM PEFR (N = 218 participants; MD 10.70 L/min, 95% CI 2.41 to 18.99; Analysis 1.5) were reported to be significantly better with anti-leukotriene in this study, but it is not clear whether the PEFR results were based on intention-to-treat or per-protocol analysis.

Asthma control and biological markers of inflammation

No other included paediatric trials reported other secondary efficacy outcomes. However, the sponsor of one cross-over trial (Simons 2001) provided certain data, which we presented in Table 1 RevMan can not calculate correct treatment effects and 95% CI from such data unless the results of paired t-tests are provided to allow for the within-participant correlation of the treatment effects, so we did not present forest plots for these outcomes.

There was no statistically significant group difference observed in children and adolescents with exacerbations requiring oral corticosteroids over 16 weeks (N = one trial: 182 participants; RR 0.82, 95% CI 0.54 to 1.25; Analysis 2.1; Figure 4). We estimated the number of children who had one or more exacerbations requiring a course of oral corticosteroids by subtracting the number reported as having a second course of oral corticosteroids from the total number of courses on each treatment for one trial (Lemanske 2010). Because of lack of trials reporting the primary outcome, we did not perform subgroup analysis, funnel plot, and sensitivity analysis.

Summary of main results

In children who remain symptomatic with low-dose ICS, there were insufficient data to determine the effect of adding anti-leukotrienes to ICS on the number of participants with one or more exacerbations requiring oral corticosteroids. There were no data on secondary efficacy outcomes to derive any firm conclusion favouring either strategy, whether comparing the same dose or a higher-dose ICS. The limited available data revealed no significant group difference in withdrawals and safety profile, but did not meet the criteria of equivalence. No trial explored the addition of anti-leukotrienes as a strategy to taper the dose of ICS. The paucity of paediatric trials in this area and the inconsistent measurement of key outcomes preclude firm conclusions regarding the efficacy and safety of adjunctive anti-leukotriene agents in children.

Only one trial in each protocol (Lemanske 2010; Simons 2001) reported the number of participants requiring rescue oral corticosteroids. In both cases, there was no statistically significant group difference. The wide confidence intervals did not demonstrate equivalence. In the comparison testing the combination of anti-leukotrienes and ICS versus the same dose of ICS alone (step 3 versus step 2), a cross-over trial (Simons 2001) evaluated certain secondary efficacy outcomes, including lung function parameters (FEV₁ and PEFR), change in use of rescue medication, and quality of life. We could not use this data in RevMan as we did not have information on the within-participant correlation between the treatment periods. In the comparison examining the combination of anti-leukotrienes and ICS versus a higher dose of ICS (step 3 versus step 3), a cross-over trial (Lemanske 2010) reported both the main outcome and participants with exacerbation requiring hospital admission; no other secondary efficacy outcomes were reported. In other words, insufficient reporting prevented the aggregation of efficacy data in all protocols.

In both treatment protocols, the only safety outcome that we could aggregate was overall withdrawal; no significant group difference was observed with wide confidence intervals. No serious adverse events were observed in these small studies.

In view of the paucity of trials and inadequate reporting, there is inconclusive evidence to support the use of anti-leukotrienes as adjunct therapy to ICS (step-3 option) in children and adolescents (no data on preschoolers). Limited data on withdrawals prevent firm conclusions as to the safety of this strategy compared to using the same dose (step 2) or a higher dose (step 3) ICS alone.

Overall completeness and applicability of evidence

Of note is the strikingly low number of paediatric studies examining the best step-up therapy with anti-leukotrienes in children inadequately controlled with a low daily maintenance dose of ICS. We excluded four paediatric trials because we could not confirm that children were insufficiently controlled or because they included either well-controlled children on daily ICS or participants naive to ICS (Finn 2000; Jat 2006; Karaman 2007; Miraglia del Giudice 2007). Moreover, of the five eligible trials, one did not contribute data in the format required. Of interest, the only study (Strauch 2003) evaluating the clinical efficacy on bronchial inflammation, of adjunct treatment with leukotriene receptor antagonists in children with asthma on ICS, showed a significant reduction in airway inflammation and improved quality of life.

We identified only five eligible paediatric trials: The trials recruited 559 children, aged six years and above, and adolescents. No trial focused on preschoolers. Of the included studies, four trials reported only a limited number of outcomes of interest. The majority of secondary outcomes were measured as end of treatment values rather than change from the baseline, thus, limiting the interpretation of findings. We emphasise the need for further trials with complete reporting of efficacy outcomes, specifically exacerbations requiring rescue oral corticosteroids, hospital admission, and change from baseline in asthma control parameters.

Quality of the evidence

Our confidence in the effect estimates is limited by statistical imprecision due to the low number of studies and low power of our analysis.

Potential biases in the review process

There were insufficient data to assess the potential for bias relating to study quality and publication bias.

Agreements and disagreements with other studies or reviews

The Cochrane review on addition of anti-leukotriene agents to ICS for chronic asthma in children and adults published in 2004 concluded that in symptomatic people, the addition of licensed doses of anti-leukotrienes to ICS resulted in a non-significant reduction in the risk of exacerbations requiring systemic steroids (RR 0.64, 95% CI 0.38 to 1.07) with modest improvement in lung function (PEFR MD 7.7 L/min, 95% CI 3.6 to 11.8) and a decrease in the use of rescue short-acting beta₂-agonist use (MD 1 puff/week, 95% CI 0.5 to 2). With only 3 trials comparing the use of licensed doses of anti-leukotrienes with increasing the dose of ICS, no firm conclusion could be drawn about the equivalence of both treatment options (Ducharme 2004).

The prior review was heavily weighted towards adults and did not firmly conclude on the efficacy and safety of addition of anti-leukotrienes to ICS. The current review supports the same conclusion in paediatrics.

There is insufficient evidence to support the use of anti-leukotriene agents as step-3 therapy in children and adolescents with mild to moderate asthma. Despite the fact that anti-leukotrienes have been licensed for over 10 years for children in many countries, there are major limitations with the evidence base: There is an appalling paucity of paediatric trials, an absence of data on preschoolers, and the reporting of clinically relevant outcomes is highly variable. These limitations prevent firm conclusions. At present, there is no firm evidence to support the efficacy and safety of anti-leukotrienes as add-on therapy to ICS as a step-3 option in the therapeutic arsenal for children with uncontrolled asthma symptoms on low-dose ICS. Consequently, should a clinician wish to add anti-leukotrienes to the therapeutic regimen, it should be considered as a therapeutic trial and the clinical impact on asthma control and exacerbations should be documented in the specific person before considering prolonged therapy.

Implications for research

We emphasise the urgent need for further paediatric trials (including preschoolers) with sub-optimal asthma control on inhaled corticosteroids, comparing the addition of anti-leukotriene agents to existing ICS to either the same or a higher ICS. We call for complete reporting of efficacy outcomes, especially with regard to people with one or more exacerbations requiring rescue oral corticosteroids, hospital admissions, and change from baseline in asthma control indices. We also suggest considering the following issues while designing a paediatric trial:

children with mild to moderate persistent asthma incompletely controlled on daily inhaled corticosteroids;

including all paediatric age groups, including preschool-aged children;

favouring a parallel group design with a minimum of 24-week treatment duration;

Dr Bhupendrasinh Chauhan wrote the protocol, reviewed the literature search until January 2013, identified and reviewed all citations for relevance, reviewed methodological quality, extracted data, analysed and interpreted the results of the meta-analysis, wrote all versions of the manuscript, and approved the final version of the manuscript.

Prof Francine Ducharme supervised and approved the protocol, verified the extracted data, provided input in case of disagreement regarding the inclusion of trials, reviewed the methodological assessment and the interpretation of data, edited all versions of the manuscript, and approved the final version of the manuscript.

Internal sources

No sources of support supplied

External sources

Professor Francine Ducharme, Canada.

has received travel support, research funds, and fees for speaking from GlaxoSmithKline, Novartis, and Merck Frosst Inc, producer of montelukast. She has received some travel support for meeting attendance, a research grant, and consulting fee from Merck, producer of some inhaled corticosteroids preparation to which anti-leukotriene agents have been compared.

Dr Bhupendrasinh Chauhan, Canada.

received a postdoctoral scholarship from the Canadian Institute of Health Research, Canada.

Raja Ben Salah, Canada.

received a scholarship from the Canadian Institute of Health Research, Canada.

Stelmach 2002 {published data only}

Stelmach I, Jerzynska J, Kuna P. A randomized, double-blind trial of the effect of glucocorticoid, antileukotriene and beta-agonist treatment on IL-10 serum levels in children with asthma. Clinical and Experimental Allergy2002;32(2):264-9.

Weiss 2010 {published data only}

Weiss KB, Gern JE, Johnston NW, Sears MR, Jones CA, Jia G, et al. The back to school asthma study: the effect of montelukast on asthma burden when initiated prophylactically at the start of the school year. Annals of Allergy, Asthma & Immunology2010;105(2):174-81.

GINA 2011

Heuck 2000

Heuck C, Heickendorff L, Wolthers OD. A randomized controlled trial of short term growth and collagen turnover in asthmatics with inhaled formoterol and budesonide. Archives of Disease in Childhood2000;83(4):334-9.